The automotive industry is developing catalytic converters for treating exhaust gases developed in an internal combustion engine. Some newer forms of these catalyst converters include a pair of spaced apart catalyst beds. The first bed in the catalyst converter is a three-way catalytic converter which simultaneously treats oxides of nitrogen, carbon monoxide and unburned hydrocarbons. Generally, the gases flowing across this bed are derived from an engine operating near or at a stoichiometric air to fuel ratio so that the resulting exhaust gases have an overall reducing potential. The reducing potential is favored over the three-way catalyst in order to eliminate oxides of nitrogen. The second catalyst bed in the converter is an oxidation catalyst bed for eliminating any unburned hydrocarbons or carbon monoxide remaining in the exhaust gas stream. Such a catalyst bed is best operated under oxidizing conditions. Therefore, it is necessary to introduce secondary air to the exhaust gas stream after it has passed through the first three-way catalyst and prior to its passage over the oxidation catalyst. Primary air is the air which is mixed with the fuel which is burned in the internal combustion engine.
It is a principal object of this invention to provide a secondary air introduction system between the three-way catalyst and the oxidation catalyst which is extremely efficient in operation but yet of simple and practical design.
A novelty study conducted on the subject matter of this application resulted in the citation of the following U.S. Pat. Nos. 3,061,416; 3,413,096, 3,656,915; 3,719,457; 3,773,894 and 3,813,226.